The present invention relates in general to spark plug assemblies for internal combustion engines, and more particularly to the construction of spark plug housing adapters for each cylinder of multi-cylinder internal combustion engines providing an ignition or mini-combustion chamber formed by a portion of the adapter immediately surrounding the electrodes of the spark plug for ignition of raw fuel or a rich combustible mixture producing flame for readily igniting a lean combustible mixture.
Heretofore, it has been known that a relatively lean combustible mixture designed to maximize gasoline mileage in internal combustion engines is frequently difficult to ignite and often does not burn completely. This results in frequent misfiring or failure to fire the lean combustion mixture in the main combustion chambers of the internal combustion engines using them and also increases the air pollution caused by the exhaust from the internal combustion engine, both due to failure of ignition when this occurs and also due to failure of the mixture to burn completely even though ignition may occur.
Some efforts to reduce air pollution resulting from noxious gases in the exhaust of internal combustion engines have involved addition of air injection pumps to the internal combustion engine, exhaust recycling systems to cut down the formation of smog producing chemicals, and use of catalytic converters fitted into the exhaust system of the automobile to convert harmful constituents of the engine exhaust into harmless chemical components or compositions. All of these measures involve adding on of additional or auxiliary devices to automobiles, and in most cases have reduced the gasoline mileage attainable, thus increasing the consumption of fuel energy and further compounding the already difficult energy consumption problem.
Efforts have been made to achieve greater fuel economies in internal combustion engines and concurrently obtain greater reliability of ignition and more complete combustion by redesigning the engine block to define a smaller auxiliary combustion chamber or ignition chamber communicating with each respective main combustion chamber with a spark plug associated with each auxiliary combustion chamber having its electrode gap in the auxiliary combustion chamber and with a valved fuel supply line to the auxiliary combustion chamber providing a rich fuel-air mixture to the auxiliary combustion chamber for reliable ignition and a second fuel mixture supply conduit supplying a lean fuel-air mixture to the main combustion chamber. Examples of such arrangements are found in the earlier U.S. Pat. Nos. 3,844,259 and 3,853,097 granted to Honda Motor Co., Ltd. In such prior art systems the rich air-fuel mixture is supplied through an intake valve to the auxiliary combustion chamber specially formed in the engine block during the downstroke or suction stroke of the piston for the associated cylinder, and the rich mixture which is readily ignited by the associated spark plug produces a flame discharge communicating with the lean mixture supplied to the main combustion chamber during the same suction stroke of the piston to achieve more reliable ignition and more complete combustion of the lean mixture. However, the designs employed in those prior patented systems require specially formed engine blocks designed so that the configuration of the engine block provides for the auxiliary combustion chamber or ignition chamber in which ignition of the rich fuel-air mixture occurs to produce the flame which achieves ignition of the lean fuel-air mixture in the main combustion chamber. That system of ignition is not adaptable for use in already existing conventional internal combustion engine blocks, because new engine blocks would be required to provide the special auxiliary combustion chamber configuration and valved rich mixture intake supply system needed in those prior art designs. More recently, spark plug assemblies of the construction shown in U.S. Pat. Nos. 4,006,725 and 3,926,169 have been proposed having a valved passage for a readily ignitable charge of fuel and air to achieve ignition of the lean fuel-air mixture in the main combustion chamber, but better metering of the fuel charge admitted through the valved passage is desired.
An object of the present invention is the provision of a novel replacement spark plug assembly for internal combustion engines wherein the replacement spark plug assembly incorporates an apertured dome structure forming a mini-combustion chamber surrounding the electrode gap to define an auxiliary ignition chamber and includes within the assembly a valved intake conduit for communication with a raw fuel source to admit an accurately metered charge of the raw fuel to the auxiliary ignition chamber to achieve ignition and production of flame for igniting a lean fuel mixture in the main combustion chamber of the associated engine cylinder.
Another object of the present invention is the provision of a novel spark plug adapter unit which may be fitted into conventional automobile engine heads in place of the standard spark plug and provide for ignition of a metered quantity of raw fuel in a limited size ignition chamber defined at the electrode gap of a spark plug to produce flame for ensuring ignition and more complete burning of a lean fuel-air mixture in the combustion chamber of the associated engine cylinder.
Another object of the present invention is the provision of a novel spark plug assembly as defined in either of the two preceding paragraphs, wherein ports in the walls of the mini-chamber communicating with the main combustion chamber provide air flow from the latter into the mini-chamber during the compression stroke of the associated piston to produce a turbo-action within the mini-chamber for maximum atomization of raw fuel admitted through the valved intake conduit, and a mini-piston and movable disc coact to properly meter the raw fuel charge.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings showing a preferred embodiment of the invention.